Method for two phase conveyance of a product

ABSTRACT

The present invention is directed to a method and apparatus for conveying a product. In accordance with the method aspects of the present invention, the steps comprise providing a flow channel having internal surfaces and introducing the product into the channel and causing the product to move through the channel for flow as a first phase through the channel. Pursuant to a feature of the present invention, a step of simultaneously applying a film of fluid over the internal surfaces is carried out during movement of the product through the channel to provide a second phase to surround the first phase and separate the first phase from the internal surfaces during conveyance of the product through the channel so that the first phase moves as a plug of material through the channel.

This application is a continuation of application Ser. No. 08/023,997,filed on Feb. 26, 1993, now U.S. Pat. No. 5,393,546.

FIELD OF THE INVENTION

The present invention is directed to a product conveyance method andapparatus, the apparatus being suitable for use as an extrusion die forconveying and forming a product. More specifically, the presentinvention is directed to a method and apparatus for a two phase productconveyance method and apparatus arranged to reduce shear forces exertedon the product during conveyance.

BACKGROUND OF THE INVENTION

The need to convey a product is frequently encountered during manyindustrial processes. For example, an extruder is a well known apparatusutilized to provide continuous mixing and conveyance of ingredients of aproduct. Extruders are widely used in many industries, e.g. the chemicaland food processing industries, to continuously mix ingredients of aproduct and to form the product by conveying the mixed ingredientsthrough a die having a preselected shape. The continuous processingprovided by an extruder often results in an efficient and cost effectivealternative to batch processing techniques.

Extruders typically include an arrangement of inlet ports for ingress ofvarious ingredients to be mixed by the extruder, into a mixing chamber.The mixed ingredients are forced through the extrusion die by theconveying action of various mechanical elements and onto a conveyor orother processing mechanism for cutting and further processing. Thecross-section of the extrusion die is arranged to form the mixedingredients (referred to as the extrudate), as it is forced through thedie, into a desired shape for the product.

Conveyance of a mixture of ingredients through a die often occurs underlaminar flow conditions. Product flow under these conditions causesmaximum flow velocity at the center of flow, with those portions of theproduct in contact with surfaces, such as, e.g., extruder die surfaces,tending to adhere to the surfaces due to the friction. In suchcircumstances, it is typical for the surfaces of the mixed ingredientsin contact with the surfaces of the extruder die to encounter frictiondue to the relative movement of the product over the extruder surfaces.This results in shear forces throughout the product as it is conveyedthrough the extruder and forced through the extrusion die.

The presence of laminar flow with shear forces can degrade productquality. This is particularly true in shear sensitive products, i.e.,products that are susceptible to degradation due to the shear forces.Thus, the advantages of continuous mixing and conveying afforded byextrusion processing can be overcome by product degradation when appliedto a shear sensitive product, particularly when the shear sensitiveproduct is of a relatively high viscosity. Moreover, the shear forcescan cause physical break up of the product as it is forced through anextrusion die, resulting in degradation of the internal structure andintegrity of the product.

In certain ingredient mixing operations, desired chemical reactionsoccur between the ingredients. Often the chemical reactions affect therheological properties of the product. For example, a setting solutioncan be mixed with other liquid ingredients to set the ingredients into asolid or gel state for shaping and forming. Setting reactions are alsoutilized to reconstitute food products so that solutions, e.g.,containing a source ingredient, can be reconstituted into a gel havingthe texture and consistency of the original food product used to providethe source ingredient.

A problem with utilizing a continuous extrusion process to obtain a setextrudate is that when the product begins to set within the extruder,the possibility of degradation and physical break up of the extrudateduring conveyance increases after the transition of the mixedingredients from a liquid phase to a highly viscous solid or gel phase.The high viscosity of the setting gel increases shear forces throughoutthe extrudate as it is conveyed through the extruder. When the finalmixture of the product is shear sensitive, the extrudate tends todegrade and break apart, at least sporadically, as it is conveyedthrough the extrusion die, significantly limiting the ability tocontinuously convey, shape, form and cut the extrudate in an efficientand continuous manner.

Thus, the desirability and efficiency of continuously processing andconveying ingredients undergoing a simultaneous chemical settingreaction becomes problematical, particularly in an extrusion process.The inherent continuous mixing, conveying, forming and shaping aspectsof an extrusion operation are rendered ineffective for shear sensitiveproducts, especially those undergoing setting reactions, due to acontinuously increasing viscosity and resultant generation of damagingshear forces, as the mixed ingredients transition during conveyancethrough the extruder, from a liquid phase to a solid phase. Heretoforeknown systems do not provide a method of product conveyance suitable toreduce shear forces so that, e.g., an extrusion process of the typedescribed above, can be effectively performed.

SUMMARY OF THE INVENTION

The present invention is directed to an improved method and apparatusfor conveyance of a product. Generally, the present invention comprisesa conveyance channel to receive and convey the product. The conveyancechannel is provided with internal surfaces forming flow surfaces forconveyance of the product through the channel. A fluid flow pathcommunicating with the internal surfaces is arranged to continuouslyapply a film of fluid over the internal surfaces as the product isconveyed through the channel so that the product is conveyed as a firstphase within the channel surrounded by the film acting as a second phaseto separate the first phase from the internal surfaces.

According to a feature of the present invention, the second phase fluidfilm comprises a low viscosity fluid to minimize friction between theproduct being conveyed and the internal surfaces of the conveyancechannel. This minimizes the development of shear forces within theproduct. Indeed a low viscosity second phase film permits the firstphase product to flow through the conveyance channel as a plug ofmaterial, i.e. a mass of material flowing uniformly in a unitary masswith minimal relative velocity between portions or layers of the firstphase.

In an exemplary embodiment of the present invention, the internalsurfaces of the conveyance channel comprise a porous material and thefluid flow path surrounds the porous material on a side thereof oppositeto the internal surfaces, to cause the fluid to flow through the porousmaterial and form the film on the internal surfaces for two phase flowaccording to the present invention.

For use in an extrusion process including the continuous extrusionforming of a product undergoing a simultaneous chemical settingreaction, as described above, the present invention comprises a methodand apparatus for first continuously mixing and, immediately thereafter,extrusion conveyance and shaping of reactant ingredients. The reactantingredients are thoroughly mixed by mechanical action in anextruder-type mixer mechanism and simultaneously conveyed to anextrusion die while still in a liquid phase. The extrusion die isarranged so that the length of the zone and the speed of conveyance ofthe mixed reactant ingredients through the zone permit an adequateamount of time for the mixed reactant ingredients to react chemicallywith one another and to thereby set in a solid or gel state forextrusion and further processing. Once in the solid or gel state, thereactant ingredients continue flow as a plug due to the minimal shearforces resulting from the effects of the surrounding second phase fluidfilm. The shape of the extrusion die is configured to the desired shapefor the set extrudate so that the solid or gelled product sets in thedesired shape as it is continuously moved through the extrusion die.

The film of low viscosity fluid provides a lubrication function byseparating the high viscosity, setting ingredients from direct, frictionengagement with the extrusion die surfaces. Relatively high frictionmotion between the solidifying ingredients and the surfaces of theextrusion die is replaced by relatively low friction engagements oneither side of the low viscosity film.

In an exemplary embodiment of the present invention, the settingreaction can be delayed until after the reactant ingredients have flowedfrom the mixer mechanism into the conveyance channel. This can beachieved by setting the dimensions of the conveyance channel so thatback pressure within the mixer mechanism is sufficiently high topreclude setting reactions. Once the reactant ingredients are within theconveyance channel, the plug type movement of the reacting ingredients,as the first phase, facilities an efficient and effective settingreaction between reactant ingredients due to the minimal relative motionand shear between layers of the plug resulting from the surrounding lowviscosity second phase film.

Thus, the efficiency of continuous extruder conveyance after mixingreactant ingredients that cause gelling, can be utilized due to the twophase conveyance method of the present invention without encounteringpotentially deleterious effects of degrading shear forces in the productflow after the setting of the product in a solid or gel state.

In one exemplary embodiment of the extrusion feature of the presentinvention, the surfaces of the extrusion die comprise porous flowsurfaces. A system of fluid channels is formed in a housing arranged tomount the extrusion die. A fluid inlet is formed in the housing and asystem of reservoirs is arranged within the housing to surround theporous flow surfaces. The fluid channels provide fluid communicationbetween the fluid inlet and the reservoir system.

In this manner, the low viscosity fluid is formed into a uniform filmover the ingredient contacting surfaces of the extrusion die byinjection of a pressurized flow of the low viscosity fluid into theinlet, which then flows under pressure through the fluid channels andinto the reservoir system. The reservoirs are configured so that fluidunder pressure within the reservoir system continuously seeps in agenerally uniform flow through the porous material and onto theingredient contacting surfaces of the extrusion die. A continuousinjection of the pressurized low viscous fluid is maintained while thesetting product moves through the extrusion die to maintain acontinuously lubricating film between the die surfaces and the movingproduct for a two phase flow.

In accordance with another advantageous feature of the presentinvention, the low viscous fluid comprises a setting solution to improvethe setting of the mixed ingredients at the surfaces thereof in contactwith the second phase film. Thus, the setting chemical reaction isreinforced at the moving surfaces of the mixed ingredients by the lowviscosity fluid as it lubricates the extrusion die surfaces to minimizeshear forces in the setting product. Moreover, the chemical reactionbetween the second phase film and the surfaces of the first phase plugcauses the surfaces of the plug to set or gel more quickly than theremaining portions of the plug. The set or gelled plug surfaces act toinhibit the transfer of any surface shear forces that may develop to theinterior of the plug, to further minimize the effects of shear forces onthe setting of the reactant ingredients within the plug.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an extruder system utilizing a twophase flow conveyance according to the present invention.

FIG. 2 is a side, partial cross-sectional view of the extrusion die ofFIG. 1.

FIG. 3 is an end view of the extrusion die of FIG. 2, taken along line3--3 of FIG. 2.

FIG. 4 is a side view of the inside mandrel of the extrusion die of FIG.2.

FIG. 5 is a top view of the spider section of the mandrel of FIG. 4.

FIG. 6 is a process flow chart of an example of the present invention.

DETAILED DESCRIPTION

Referring now to the drawings, and initially to FIG. 1, there isillustrated an extrusion system according to the two phase flowconveyance of the present invention, generally indicated by thereference numeral 10. The system 10 comprises a mixer 12 of e.g., thetype manufactured by Mondomix-Holland by of Nederhorst den Berg, theNetherlands. The mixer 12 includes two inlet ports 14, 16, each coupledto a pump 18, 20, respectively. The pump 18 is coupled to a first supplytank 22 and the pump 20 is coupled to a second supply tank 24. In thismanner, the pumps 18, 20 are operated simultaneously to inject thecontents of the tanks 22, 24 into the respective inlet ports 14, 16 ofthe mixer 12 for mixing.

In an exemplary embodiment of the present invention, a slurry orsolution to be set, shaped and formed is contained in the first supplytank 22 and a setting solution is contained in the second supply tank24. The operation of the pumps 18, 20 and the mixer 12 causes thesolution of the first supply tank 22 to be thoroughly mixed with thesetting solution and conveyed to an outlet channel 26. Pursuant to thepresent invention, the outlet channel 26 is directly coupled to anextrusion die 28.

As illustrated in FIG. 1, the extrusion die 28 is arranged adjacent to aconveyor 30 so that an extrudate exiting from the extrusion die 30 canbe conveyed to other mechanisms for further processing (not shown). Acutting mechanism (not shown) can also be mounted between the extrusiondie 28 and conveyor 30 to cut the extrudate as it exits the extrusiondie 28, as is generally known in the art.

A fluid inlet port 32 is coupled by a tube 34 to a pump 38, which is, inturn, coupled to a third supply tank 36 via a tube 40. The third supplytank 36 contains a low viscosity fluid that is pumped into the inlet 32by the pump 38 to facilitate low shear force flow for the extrudate, aswill be described below.

As should be understood, the thorough mixing in the mixer 12 of thesolution input from the first supply tank 22 and the setting solutioninput from the second supply tank 24, results in a chemical reactioncausing the mixture to gel. Thus, the mixture undergoes a phasetransition during conveyance through the extrusion die 28 and prior toegress of the mixture as a gelled extrudate.

To that end, the pumps 18, 20 and the mixer 12 are operated to achieve aspeed of conveyance through the mixer 12 and to the extrusion die 28 sothat the solutions from the tanks 22, 24 are input to the mixer 12,thoroughly mixed and transported to the extrusion die 28, while themixture remains in a liquid phase. The pumps 18, 20 and the mixer 12 arealso operated to achieve mixing and conveyance of the mixture, which canbe in an aqueous slurry phase, under a pressure sufficient to force themixture into and through the extrusion die 28 for egress of the mixture,as the extrudate from the extrusion die 28. The dimensions of the die 28can be fixed so that back pressure in the mixer 12 is sufficiently highto prevent the starting of the setting reaction until the mixture flowsinto the die 28.

Moreover, the extrusion die 28 is configured to have a length sufficientto permit solidification of the mixed components during conveyancethrough the die so that the extrudate is in a gel state suitable forcutting and processing upon egress from the extension die 28. Inaddition, the cross-section configuration of the extrusion die 28 isformed to mold the solidifying mixture into a desired shape, as themixed components or ingredient materials flow through the die.

Referring now to FIG. 2, there is illustrated a side, partialcross-sectional view of the extrusion die 28. In the exemplaryembodiment of the present invention, the extrusion die 28 comprises agenerally cylindrical, plastic die body 42. A longitudinally extendingchannel 44 is formed throughout the entire length of the die body 42 toprovide product ingress and egress openings 46, 48, respectively. Thechannel 44 includes a portion 49 of expanded diameter at the productingress end 46 of the die body 42. The internal surfaces 50 of theportion 49 are threaded to secure a cylindrical top cap 52 to the diebody 42.

To that end, the top cap 52 includes an axially extending, threadedelement 54 removably, and threadedly engaged with the internal surfaces50 to secure the cap 52 to the die body 42, as illustrated in FIG. 2.

A first cylindrical porous sleeve 56 is received into the channel 44 andextends from the product egress opening 48 of the die body 42 to thelower end of the enlarged portion 49. The porous sleeve 56 can comprisea food grade polyethylene material manufactured by Porex TechnologiesCorporation, including various pore sizes, as, e.g., 20, 35, 60, 125,250 or 350 micron pore sizes. In the exemplary embodiment of the presentinvention, a 20 micron pore size material is used to form the poroussleeve 56.

Moreover, a plastic spider/mandrel element 58 is arranged to extendwithin the channel 44 in a co-axial relationship to the porous sleeve56. The spider/mandrel element 58 mounts a second cylindrical poroussleeve 60, spaced from the first cylindrical porous sleeve 56 and madefrom a similar material as used to form the first porous cylindricalsleeve 56. The spaced first and second cylindrical porous sleeves 56, 60define an annular, product flow space 61, extending between the firstand second porous sleeves 56, 60 from the enlarged portion 49 to theproduct egress opening 48 of the die body 42. The annular space 61 isillustrated in FIG. 3.

A side view of the spider/mandrel element 58 is illustrated in FIG. 4.The element 58 comprises a spider section 62 and an integral mandrelsection 64. The spider section 62 is cylindrical in shape and isdimensioned to have a diameter substantially equal to the inner diameterof the enlarged portion 49. The spider section 62 is received within theenlarged portion 49 and rests upon the lower end thereof, as mostclearly illustrated, in phantom, in FIG. 2. A circumferentiallyextending groove 66 is formed in the outer circumference of the spidersection 62 and a setting solution channel 68 is formed within thespider/mandrel element 58, extending along the axis of the element 58,from a region axially aligned with the upper end of thecircumferentially extending groove 66 to the lowermost end of themandrel section 64.

Referring briefly to FIG. 2, a plug 69 is received within an openingformed within the die body 42 and is arranged to extend to within thecircumferentially extending groove 66 to secure the element 58 withinthe die body 42.

A series of radially extending fluid flow holes 70 is arranged in thespider section 62 to provide fluid communication between thecircumferentially extending groove 66 and the setting solution channel68 (see FIG. 5). Moreover, a series of openings 72 is formed through themandrel section 64, with each opening 72 providing fluid communicationbetween the setting solution channel 68 and the outer surface of themandrel section 64. As clearly illustrated in FIG. 4, the mandrelsection 64 includes a plurality of circumferentially extending, raisedportions 74 to provide a series of recessed surface areas 76 on theouter surface of the mandrel section 64. As should be understood, therecessed surface areas 76 and second cylindrical porous sleeve 60 definea series of axially spaced, annular shaped reservoirs to receive fluidfrom the channel 68 via the openings 72.

Referring once again to FIG. 2, a setting solution feed channel 78 isformed within the die body 42 and extends along a direction parallel toeach of the first and second cylindrical porous sleeves 56, 60. Thechannel 78 is connected to the fluid input port 32, which is, in turn,connected to the tube 34, as described above. The channel 78 is utilizedto force a low viscosity setting solution under pressure to surfaces ofthe cylindrical porous sleeves 56, 60, as will appear.

To that end, a fluid flow opening 80 is formed to provide fluidcommunication between the channel 78 and the circumferentially extendinggroove 66 so that a setting solution introduced into the channel 78 bythe action of the pump 38, via the tube 34 and inlet port 32, flowsthrough the channel 78, into and through the opening 80, around thecircumferentially extending groove 66, through the fluid flow holes 70and into the setting solution channel 68. The pressurized fluid flowcontinues through the channel 68, through the openings 72 and into thereservoirs defined by the recessed surface areas 76 of the mandrelsection 64 and the second cylindrical porous sleeve 60.

The pressurized fluid within the reservoirs continuously seeps throughthe porous material of the sleeve 60 to form a film of fluid on thesurface of the sleeve 60 facing the annular product flow space 61.

In a similar manner, a series of fluid flow openings 82 provide fluidcommunication between the channel 78 and corresponding ones of a seriesof cut out sections 84. Each cut out section 84 extends around theentire outer circumference of the first cylindrical porous sleeve 56,with the cut out sections 84 together covering a substantial portion ofthe outer surface of the sleeve 56. Thus, fluid flow in the channel 78also flows through the openings 82 and into the sections 84 from whichthe fluid continuously seeps uniformly through the first cylindricalporous sleeve 56 to form a film of fluid on the surface of the sleeve 56facing the annular flow space 61.

The top cap 52 includes a product inlet port channel 86 to receive theoutlet channel 26 of the mixer 12. The lowermost end of the threadedelement 54 is spaced from the top surface of the spider section 62. Inthis manner, the mixture of materials flows from the outlet channel 26,through the inlet port channel 86 to within the space defined by thethreaded element 54 and the top surface of the spider section 62.

Referring to FIG. 5, the top surface of the spider section 62 is formedto include a series of kidney-shaped holes 88, each aligned above theannular space 61 when the spider/mandrel element 58 is mounted withinthe die body 42. Accordingly, the mixture within the space between thethreaded element 54 and the top surface of the spider section 62 flowsthrough the kidney-shaped holes 88, into the annular product flow space61 and out the egress opening 48. As should be understood, the films offluid formed on the surfaces of the first and second cylindrical poroussleeves 56, 60 separate the mixture from the surfaces of the extrusiondie 28 as the mixture flows through the annular space 61.

FIG. 6 is a process flow chart of an example of the operation of theabove described apparatus utilized to form structured onion rings. Tothat end, the solution in the first supply tank 22 comprises a freshonion slurry having the following formulation:

    ______________________________________                                        "A" SLURRY                                                                    INGREDIENTS                                                                   ______________________________________                                        Fresh Onion Puree       60.00%                                                Water                    6.64%                                                Manugel DMB, Alginate    1.50%                                                Sugar                    1.86%                                                Subtotal                  70%                                                 ______________________________________                                    

The setting solution contained in the second supply tank 24 comprises aslurry having the following formulation:

    ______________________________________                                        "B" SLURRY                                                                    INGREDIENTS                                                                   ______________________________________                                        Water                    23.55%                                               Starch                    2.00%                                               Rice Flour                2.00%                                               Sugar                     1.10%                                               Calcium Sulfate Dehydrate                                                                               .91%                                                Salt                      .25%                                                Potassium Sorbate         .10%                                                Xanthan Gum               .05%                                                Sodium Hexametaphosphate  .04%                                                Subtotal                   30%                                                ______________________________________                                    

The percentage listed next to each ingredient in the above formulationsrepresents the percentage, by weight, of the corresponding listedingredient, in the final mixture of the fresh onion slurry and settingsolution, upon mixing within the mixer 12. Thus, the subtotals for the"A" and "B" slurries represent the percentage by weight of each slurryin the final mixture.

As illustrated in the process flow chart of FIG. 6, fresh onion isinspected, washed, peeled, pureed and hot blanched. A pre-blended drymixture of sodium alginate and sugar is mixed with water and then mixedwith the fresh onion puree, in the percentages by weight indicatedabove, to form a wet mixture fed into the inlet port 14 by the pump 18.As indicated in FIG. 6, the pH level of the fresh onion wet mixture canbe adjusted empirically so as to control the setting reaction time.Lactic acid can be used as an additive to vary the pH level of the "A"slurry.

The "B" slurry comprises a wet mixture formed by mixing water with apre-blended dry mix consisting of starch, rice flour, sugar, salt,calcium sulfate dihydrate, sodium hexamethaphosphate, keltrol BT andpotassium sorbate, in the percentages by weight indicated above. Thesetting reaction time can also be controlled by empirically adjustingthe level of sodium hexamethaphosphate in the pre-blended dry mix.

As described above, the reaction time and fluid flow rates of the pumps18, 20 are adjusted to achieve a thorough mixing of the "A" and "B"slurries in the mixer 12 without the setting reaction causing the mixedslurries to gel until the product flow enters the extrusion die 28.Gelling occurs through the occurrence of primary internal chemicalreactions including reactions between calcium ions provided by thecalcium sulfate dihydrate, and sodium alginate to form calcium alginategel.

As illustrated in FIG. 6, the "A" and "B" slurries are input to theextruder (mixer 12) and flow from the extruder, after mixing, into theextrusion die 28. The low viscosity setting solution fed under pressureinto the inlet port 32 comprises a solution of water, calcium lactate,lactic acid and sugar to form a thin liquid film on the surfaces of thecylindrical porous sleeves 56, 60, as described above. In addition, thecalcium lactate provides an additional source of calcium ions thatpenetrate the mixture of the "A" and "B" slurries, by diffusion from thefilm. Of course, as described above, the film also provides a two phase,nearly shear stress free movement of the solidifying mixture of theslurries as it flows through the extrusion die 28 to the egress end 48of the die body 42.

What is claimed is:
 1. A method for conveying a product, comprising thesteps ofproviding a flow channel having internal surfaces; introducingthe product into the channel and causing the product to move through thechannel for flow as a first phase through the channel; andsimultaneously applying a film of fluid over the internal surfaces toprovide a second phase to surround the first phase and separate thefirst phase from the internal surfaces during conveyance of the productthrough the channel, wherein the product comprises a mixture ofchemically reacting components, the chemical reaction causing themixture to gel during conveyance as the first phase prior to egress fromthe channel and wherein conveyance of the gel through the channel iseffected without encountering degrading shear forces that cause loss ofintegrity of the gel.
 2. The method of claim 1, wherein the step ofsimultaneously applying a film of fluid is carried out byforming theinternal surfaces from a porous material; and causing the fluid to flowuniformly through the porous material to the internal surfaces of theflow channel.
 3. The method of claim 1, wherein the product has a firstviscosity and the fluid has a second viscosity lower than the firstviscosity to provide a low viscosity second phase surrounding the firstphase and separating the first phase from the internal surfaces.
 4. Themethod of claim 1, wherein the fluid reacts chemically with the product.5. A method for continuously forming a product, comprising the stepsof:mixing at least two components to form a mixture; providing a flowchannel having internal surfaces; introducing the mixture of at leasttwo components into the channel and causing the mixture to move throughthe channel for flow as a first phase through the channel;simultaneously applying a film of fluid over the internal surfaces toprovide a second phase to surround the first phase and separate thefirst phase from the internal surfaces during conveyance of the mixturethrough the channel; and causing the at least two components to reactchemically with one another, resulting in a transition of the mixturefrom a fluid state to a gel, the transition occurring substantiallyafter the step of introducing the mixture into the channel so that thegel is surrounded by the film and separated from the internal surfaces,wherein conveyance of the gel through the channel is effected withoutencountering degrading shear forces that cause loss of integrity of thegel.
 6. The method of claim 5, wherein the step of simultaneouslyapplying a film of fluid is carried out byforming the internal surfacesfrom a porous material; and causing the fluid to flow uniformly throughthe porous material to the internal surfaces of the flow channel.
 7. Themethod of claim 5, wherein the components of the mixture include analginate and a source of calcium to form an alginate gel during movementthrough the flow channel.
 8. A method for continuously forming aproduct, comprising the steps of:providing a flow channel havinginternal surfaces; introducing the product into the channel and causingthe product to move through the channel for flow as a first phasethrough the channel; simultaneously applying a film of fluid over theinternal surfaces to provide a second phase to surround the first phaseand separate the first phase from the internal surfaces duringconveyance of the product through the channel; and causing the film offluid to react chemically with the product at the interface between thefirst phase and the second phase during conveyance of the productthrough the channel, wherein the product comprises a mixture ofchemically reacting components, the chemical reaction causing themixture to gel during conveyance as the first phase prior to egress fromthe channel and wherein conveyance of the gel through the channel iseffected without encountering degrading shear forces that cause loss ofintegrity of the gel.
 9. The method of claim 8, wherein the step ofsimultaneously applying a film of fluid is carried out byforming theinternal surfaces from a porous material; and causing the fluid to flowuniformly through the porous material to the internal surfaces of theflow channel.
 10. The method of claim 8, wherein the product comprises afood and the chemical reaction results in a skin structure formingaround the food at the interface between the first phase and the secondphase.
 11. A method for continuously forming a product, comprising thesteps of:mixing at least two components to form a mixture; providing aflow channel having internal surfaces; introducing the mixture of atleast two components into the channel and causing the mixture to movethrough the channel for flow as a first phase through the channel;simultaneously applying a film of fluid over the internal surfaces toprovide a second phase to surround the first phase and separate thefirst phase from the internal surfaces during conveyance of the mixturethrough the channel, wherein the at least two components chemicallyreact so as to cause the mixture to gel during conveyance as the firstphase prior to egress from the channel and wherein conveyance of the gelthrough the channel is effected without encountering degrading shearforces that cause loss of integrity of the gel.
 12. The method of claim11 wherein the at least two components comprise an alginate and a sourceof calcium to form an alginate gel during the step of causing themixture to move through the channel for flow as a first phase throughthe channel.
 13. The method of claim 11 wherein the at least twoingredients react chemically with one another.
 14. A method forconveying a product, comprising the steps ofproviding a flow channelhaving internal surfaces; introducing the product into the channel andcausing the product to move through the channel for flow as a firstphase through the channel; and simultaneously applying a film of fluidover the internal surfaces to provide a second phase to surround thefirst phase and separate the first phase from the internal surfaces tothereby cause the first phase to move as a plug of material duringconveyance of the product through the channel, wherein the productcomprises a mixture of chemically reacting components, the chemicalreaction causing the mixture to gel during conveyance as the first phaseprior to egress from the channel and wherein conveyance of the gelthrough the channel is effected without encountering degrading shearforces that cause loss of integrity of the gel.
 15. A method forcontinuously forming a product, comprising the steps of:providing amixing chamber; using the mixing chamber to mix at least two componentsto form a mixture; providing a flow channel having internal surfaces;coupling the mixing chamber to the flow channel; causing the mixture tomove from the mixing chamber to the flow channel for flow as a firstphase through the channel under conditions resulting in a back pressurein the mixing chamber; simultaneously applying a film of fluid over theinternal surfaces to provide a second phase to surround the first phaseand separate the first phase from the internal surfaces duringconveyance of the mixture through the channel; and causing the at leasttwo components to react chemically with one another, resulting in atransition of the mixture from a fluid state to a gel, the back pressurepreventing the transition of the mixture from a fluid state to a geluntil the mixture flows into the channel so that the gel is surroundedby the film and separated from the internal surfaces, wherein conveyanceof the gel through the channel is effected without encounteringdegrading shear forces that cause loss of integrity of the gel.
 16. Amethod for continuously forming a product, comprising the stepsof:providing a flow channel having internal surfaces; introducing theproduct into the channel and causing the product to move through thechannel for flow as a first phase through the channel; simultaneouslyapplying a film of fluid over the internal surfaces to provide a secondphase to surround the first phase and separate the first phase from theinternal surfaces during conveyance of the product through the channel;and causing the film of fluid to react chemically with the product atthe interface between the first phase and the second phase to form askin surface surrounding the first phase at the interface with thesecond phase during conveyance of the product through the channel,wherein the product comprises a mixture of chemically reactingcomponents, the chemical reaction causing the mixture to gel duringconveyance as the first phase prior to egress from the channel andwherein conveyance of the gel through the channel is effected withoutencountering degrading shear forces that cause loss of integrity of thegel.
 17. A method for continuously forming a product, comprising thesteps of:mixing at least two components to form a mixture; providing aflow channel having internal surfaces; introducing the mixture of atleast two components into the channel and causing the mixture to movethrough the channel for flow as a first phase through the channel;simultaneously applying a film of fluid over the internal surfaces toprovide a second phase to surround the first phase and separate thefirst phase from the internal surfaces during conveyance of the mixturethrough the channel; causing the film of fluid to react chemically withthe mixture at the interface between the first phase and the secondphase to form a skin structure around the mixture to contain the mixtureas a plug of material during conveyance of the product through thechannel, wherein the at least two components chemically react so as tocause the mixture to gel during conveyance as the first phase prior toegress from the channel and wherein conveyance of the gel through thechannel is effected without encountering degrading shear forces thatcause loss of integrity of the gel.
 18. A method for forming a gelledproduct comprising:preparing a liquid mixture of at least two componentscapable of chemically reacting to form a gel; causing the liquid mixtureto flow into a channel, and allowing the liquid mixture to form a gelledproduct in the channel during conveyance of the liquid mixture throughthe channel, while simultaneously applying a film of fluid over theinternal surfaces of the channel to surround the liquid mixture andseparate the liquid mixture from the internal surfaces of the channelduring conveyance of the mixture through the channel; wherein the flowof the liquid mixture into the channel causes the gelled product to beextruded from the channel to form a gelled extrudate having apreselected shape.
 19. The method according to claim 18 wherein thegelled extrudate is formed without break up and without loss ofintegrity of the gel.
 20. The method according to claim 18 wherein theliquid mixture flows as a first phase into the channel, wherein thechannel includes internal surfaces and wherein the method includes thestep of simultaneously applying a film of fluid over the internalsurfaces to provide a second phase to surround the first phase andseparate the first phase from the internal surfaces during conveyance ofthe product through the channel.
 21. The method according to claim 18wherein the gelled extrudate comprises pureed onion.
 22. The methodaccording to claim 21 wherein the gelled extrudate is in the shape of anonion ring.
 23. A food product obtained by a process comprising thesteps of:preparing a liquid mixture of at least two components capableof chemically reacting to form a gel; causing the liquid mixture to flowinto a channel; and allowing the liquid mixture to form a gelled productin the channel during conveyance of the liquid mixture through thechannel, while simultaneously applying a film of fluid over the internalsurfaces of the channel to surround the liquid mixture and separate theliquid mixture from the internal surfaces of the channel duringconveyance of the mixture through the channel; wherein the flow of theliquid mixture into the channel causes the gelled product to be extrudedfrom the channel to form a gelled extrudate having a preselected shape,wherein conveyance of the gelled product through the channel is effectedwithout encountering degrading shear forces that cause loss of integrityof the gel or physical break up of the gelled extrudate and wherein thegelled extrudate comprises pureed onion.
 24. The food product of claim23 wherein the gelled extrudate is formed without break up and withoutloss of integrity of the gel.
 25. The food product of claim 23 whereinthe liquid mixture flows as a first phase into the channel, wherein thechannel includes internal surfaces and wherein the method includes thestep of simultaneously applying a film of fluid over the internalsurfaces to provide a second phase to surround the first phase andseparate the first phase from the internal surfaces during conveyance ofthe product through the channel.
 26. The food product of claim 23wherein the gelled extrudate is in the shape of an onion ring.
 27. Thefood product of claim 23 wherein the at least two components of theliquid mixture include an alginate and a source of calcium to form analginate gel during conveyance of the mixture through the channel.